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The Geology of Hong Kong (Interactive On-line)
Tolo Channel Formation - Jc

The Tolo Channel Formation dominantly consists of grey to greyish white, laminated siltstones with rare sandy lenses alternating with thinly-bedded fossiliferous black mudstone containing pyritous nodules. At the type locality, 1 km northeast of Fung Wong Wat, the strata dip moderately (c. 60o) to the northwest although fossil evidence indicates they are overturned. The formation has an exposed thickness of 75 m and is faulted at its base against the Bluff Head Formation. The top of the formation is not exposed. A composite type section from the north side of Tolo Channel, where the formation was first recognized, is shown in Figure 4.2.

At Nai Chung, the Tolo Channel Formation strata are highly contorted and comprise highly cleaved, coarsely laminated siltstone alternating with finely laminated fossiliferous mudstone (Plate 4.1). At Ma Shi Chau, the strata consist of pinkish brown weathered, laminated micaceous siltstone and dip steeply to the west. They have yielded an ammonite fossil indicating a Jurassic age (Lam, 1973).